Solution : https://service.sap.com/sap/support/notes/509373 (SAP Service marketplace login required)
Key words : 
data type '/sapapo/bop_confirm_lock', oltp sales documents, credit limit block, /sapapo/bop_worklistconfirmation lock, confirmation lock' indicator, confirmation lock, /sapapo/bop, /sapapo/bopi, 'confirmation situation', backorder processing
Related Notes : 
       
| 375193 | Backorder processing: Composite SAP note on posting |